Rolling car down a hill

1. The problem statement, all variables and given/known data
A toy car has a total mass of 50 g, and rolls on freely spinning wheels, each of which can be modeled as a uniform disk of mass 1 g, and radius 2mm. What is the acceleration, a, of this toy car when it rolls without slipping down a ramp tilted at an angle of 20 degrees to the horizontal? By what factor is the toy car faster or slower than a frictionless block of the same total mass, ie what is a_car/a_frictionless?